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Lightwave Technology, Journal of

Issue 8 • Date Aug. 2003

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Displaying Results 1 - 18 of 18
  • Analysis of Brillouin frequency shift and longitudinal acoustic wave in a silica optical fiber with a triple-layered structure

    Page(s): 1779 - 1786
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (474 KB) |  | HTML iconHTML  

    We report a thorough analysis on the Brillouin frequency shift as a function of geometrical parameters in a silica optical fiber consisting of triple-layered structure, GeO2-doped core, P2O5, and F co-doped inner cladding, and pure silica outer cladding. General characteristic equations for the Brillouin frequency shift were analytically derived and analyzed for various fiber parameters. In experiments, three-layered optical fibers were fabricated and their Brillouin frequency shifts were measured in the wavelength region of 1.55 μm by a pump-probe technique. The longitudinal acoustic velocity in each layer was found significantly affected by the thermal stress as well as the dopant concentrations. We confirmed both in theory and experiment that the inner cladding of a three-layered optical fiber does provide a new degree of freedom in precise control of the Brillouin frequency shift. View full abstract»

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  • Wavelength stabilizer for telecommunication lasers: design and optimization

    Page(s): 1749 - 1757
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (637 KB) |  | HTML iconHTML  

    We introduce a novel method for the wavelength stabilization of semiconductor lasers for telecommunications. The approach is based on a wavelength-sensitive photodetector which, in a feedback system, generates an error signal apt to tune the source to the desired value. We extensively investigate the influence of various design parameters on performance figures such as tunability, steady-state error, and temperature dependence, as well as fabrication tolerances. The results are compared with standard specifications for wavelength-division-multiplexed optical communications with various channel spacings. View full abstract»

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  • Experimental demonstration of composite-packet-switched WDM network

    Page(s): 1717 - 1722
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1162 KB) |  | HTML iconHTML  

    We propose and demonstrate experimentally a novel technique for packet switching on a ring network. We use the wavelength dimension to increase the transmission line rate and a novel packet-stacking technique to add/drop packets. Packet stacking is used for transport rate multiplication and for equal loading of wavelengths on the physical layer. Packet stacking, switching, and unstacking have been successfully demonstrated on a four-node hubbed ring network serving five source-destination pairs on four wavelengths. Each wavelength was running at 1-Gb/s bit rate. View full abstract»

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  • Diffusion of moisture through fatigue- and aging-resistant polymer coatings on lightguide fibers

    Page(s): 1775 - 1778
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    In previous work the diffusion rate of water vapor through the polymer coating on optical fiber was estimated by monitoring the strength as a function of time after suddenly changing the ambient humidity. This technique is used here to measure the diffusion of moisture both into and out of two novel fiber coatings. The first specimen is a dual-coated fiber with silica particles added to its secondary coating. It is shown that the improvement in this fiber's reliability is not due to the silica particles adsorbing/absorbing the moisture. The second fiber, coated with a fluorinated polymer, was designed to have higher fatigue resistance as a result of having a lower permeability to moisture. It is found that even though this fiber had higher than normal resistance to fatigue, the diffusion of moisture through this coating was not substantially different than through typical coatings used on fibers for telecommunications applications. View full abstract»

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  • Demultiplexing using an arrayed-waveguide grating for frequency-interleaved DWDM millimeter-wave radio-on-fiber systems

    Page(s): 1735 - 1741
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB) |  | HTML iconHTML  

    The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme. View full abstract»

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  • Novel full-cycle-coupler-based optical add-drop multiplexer and performance characteristics at 40-Gb/s WDM networks

    Page(s): 1828 - 1837
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (655 KB) |  | HTML iconHTML  

    A novel configuration of an interferometric device, based on a full-cycle full (100%) coupler structure, loaded with a Bragg grating symmetrically placed into the uniform coupler waist, is proposed for use as an optical add-drop multiplexer (OADM) with simultaneously optimized add and drop actions. A general method for designing a suitable Bragg grating for optimal inscription in to the uniform coupler waist is also proposed for use in to the device design and development. The performance of the device is characterized at 40-Gb/s wavelength-division-multiplexing (WDM) networks using theoretical systems simulations and is compared directly with other alternative OADM architectures. View full abstract»

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  • Bidirectional WDM passive optical network for simultaneous transmission of data and digital broadcast video service

    Page(s): 1723 - 1727
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels. View full abstract»

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  • Boundary element method for analysis of holey optical fibers

    Page(s): 1787 - 1792
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    By using a full-vector boundary element method (BEM) based on a formulation in terms of transverse magnetic field components, holey fibers (HFs) are numerically analyzed. The BEM provides very accurate solutions with an extremely small number of unknowns. Not only the characteristics of all-silica HFs, but also those of hole-assisted lightguide fibers and field-confined HFs, are investigated and compared with each other. View full abstract»

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  • Cross-phase-modulation-induced nonlinear phase noise in WDM direct-detection DPSK systems

    Page(s): 1770 - 1774
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (339 KB)  

    In direct-detection differential-phase-shift-keying (DPSK) systems, the signal-spontaneous emission beat noise introduces phase noise due to Kerr nonlinearity. In wavelength-division-multiplexed (WDM) systems, this nonlinear phase noise comes not only from the channel itself through self-phase modulation (SPM) but also from the other channels through cross-phase modulation (XPM). In this paper, we theoretically and experimentally investigate XPM-induced nonlinear phase noise. We calculate the performance degradation of DPSK systems caused by XPM-induced nonlinear phase noise in addition to SPM-induced phase noise and experimentally verify it using a 600-km nonzero-dispersion-shifted-fiber link. View full abstract»

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  • Theoretical analysis of cladding-mode waveguide dispersion and its effects on the spectra of long-period fiber grating

    Page(s): 1838 - 1845
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (534 KB) |  | HTML iconHTML  

    A new method to control the free spectral range (FSR) of a long-period fiber grating (LPFG) is proposed and theoretically analyzed. As the refractive index decreases radially outward in the silica cladding by graded doping of fluorine, waveguide dispersion in the cladding modes was modified to result in the effective indexes change and subsequently the phase-matching conditions for coupling with the core mode in a LPFG. Enlargement of the FSR in a LPFG was theoretically confirmed. View full abstract»

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  • New Raman pump module for reducing pump-signal four-wave-mixing interaction in co-pumped distributed Raman amplifiers

    Page(s): 1742 - 1748
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1394 KB)  

    We propose a new Raman pump module that effectively reduces four-wave-mixing (FWM) nonlinear interaction among longitudinal pump modes and wavelength-division-multiplexed (WDM) signals in co-pumped distributed Raman amplifiers based on nonzero dispersion-shifted fibers (NZ-DSFs). Theory and experiments confirm that the proposed pump module structure, based on polarization- and wavelength-multiplexed Fabry-Perot lasers, allows distributed amplification with high co-propagating on-off Raman gain, providing a key technology for all-Raman-based dense-WDM ultralong-haul transmission. View full abstract»

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  • Analysis and control of transient dynamics of EDFA pumped by 1480- and 980-nm lasers

    Page(s): 1728 - 1734
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (310 KB)  

    The transient responses of Er-doped fiber amplifier (EDFA) to fast channel adding/dropping processes have been studied and analyzed. The result shows that the speed in which we can control EDFA with a feedback circuit is limited by the physical processes involved in the amplification. We demonstrated that with the combination of electrical feedforward and feedback, the power excursion caused by fast channel adding/dropping processes can be minimized. View full abstract»

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  • Optical label encoding using electroabsorption modulators and investigation of chirp properties

    Page(s): 1763 - 1769
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (895 KB) |  | HTML iconHTML  

    A novel scheme of optical label encoding by wavelength conversion based on electroabsorption modulators (EAMs) is reported. Based on the experimental observations, the chirp properties of the wavelength-converted signal are discussed and a wide dynamic range of the chirp α-parameter is found allowed. Compared with cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA), the EAM has several advantages, which make it attractive for optical label encoding or other applications as a wavelength converter. View full abstract»

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  • Electrooptic characteristics of thin-film PLZT waveguide using ridge-type Mach-Zehnder modulator

    Page(s): 1820 - 1827
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (590 KB) |  | HTML iconHTML  

    The design, characterization, and drift due to electrical bias (DC drift) of thin-film lanthanum-doped lead zirconate titanate (PLZT) waveguide is reported using a Mach-Zehnder modulator. The mechanism of the electrooptic responses based on hysteresis of the applied field is proposed to understand the behavior of the device. It is shown that the thin film exhibits a Kerr effect having a coefficient value of 5×10-18 (m/V)2. It is reported that by utilizing hydrogen-deficient dry etching, the DC drift is improved by a factor of 3.5. In addition, the verification of the operation of a PLZT-based device for more than 1400 h at 70°C is reported, for the first time. View full abstract»

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  • Dispersion compensating Raman amplifiers with pump reflectors for increased efficiency

    Page(s): 1758 - 1762
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    The effect of retroreflecting the pump in discrete Raman amplifiers is investigated. Simulations are used to estimate the increase in gain and efficiency and decrease in multipath interference due to double Rayleigh backscatter for typical module configurations. The effect of reflecting only a portion of the pump spectrum is considered. Experimental measurements confirm the expected increase in gain. Finally, the effect of pump-signal relative intensity noise transfer is investigated experimentally. View full abstract»

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  • Optimization of the optical properties of a deeply etched semiconductor electrooptic modulator

    Page(s): 1813 - 1819
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (467 KB) |  | HTML iconHTML  

    A rigorous numerical study of a deeply etched semiconductor electrooptic modulator is presented. A Laplace equation solver followed by a full-vectorial modal solution technique for general anisotropic optical waveguides, all based on the versatile finite-element method, is used to find the potential distribution, the modulating electric fields, the changes in the permittivity tensor associated with the electrooptic effect, and the different modes of propagation. In particular, the optimization of the optical properties of the modulator structure such as the half-wave voltage length product VπL and the optical losses due to the imperfectly conducting electrodes has been carefully carried out and results reported. In addition, the effect of the waveguide parameters on the microwave properties such as the microwave index nm and characteristic impedance Zc is explained. View full abstract»

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  • Two-stage Sagnac demultiplexer

    Page(s): 1808 - 1812
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (749 KB) |  | HTML iconHTML  

    Cascading a semiconductor optical amplifier (SOA)-based Sagnac interferometer with a second Sagnac stage allows significant improvement in the overall demultiplexer performance. A theoretical analysis and simulations show that the exploitation of a two-stage architecture results in a demultiplexing window sharpness and time compression. Eye-diagram and Q-factor experimental characterization at 2.5 Gb/s of the demultiplexer is presented, showing a 25% compression in time of the two-stage switching window and a 4.7 Q-factor improvement. View full abstract»

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  • A vectorial boundary element method analysis of integrated optical waveguides

    Page(s): 1793 - 1807
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1147 KB) |  | HTML iconHTML  

    In this paper, a new vectorial boundary element method is introduced and applied to the modal analysis of dielectric waveguides with piecewise homogeneous refractive indexes. The procedure, which is free of spurious modes, determines the full field distribution from the longitudinal fields at the refractive index boundaries. Singular kernels are evaluated through series solutions while the electric field discontinuity at corners is accommodated through either a grid refinement technique or a semianalytic approach. Our formalism generates propagation constants and modal field distributions for several representative refractive index profiles with far higher accuracy than standard finite-difference or finite-element procedures. View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

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Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs